1. Field of the Invention
The present invention relates to a novel ink composition and, more particularly, to an ink composition for digital textile printing, which is suitable for ink-jet printing on cellulose fiber materials.
2. Description of Related Art
Ink-jet printing is one kind of non-impact printing technology, and the required technical feature of the ink-jet printing is to provide images with sharpness and clearness. In order to obtain images with excellent printing quality, the ink used in ink-jet printing must show high light fastness, optical density, solubility, storage stability, and smoothness and ease of printing.
The ink-jet printing is applied in textile industry for many years. This method can be performed without use of a printing screen, so it is possible to save a lot of time and cost. Therefore, the ink-jet printing is suitable for production conditions of variation, small quantity, and customization, particularly.
From the application point of view, the ink for the ink-jet printing must have some unique properties that are different from general inks. The ink composition for the ink-jet printing should not only meet the requirements for viscosity, stability, surface tension, and fluidity, but also meet the requirements for color strength, fixation, fiber-dye bonding stability, and wet fastness.
The ink composition for the ink-jet printing comprises water-soluble dye or water-dispersible pigment; wherein the dye or the pigment can be soluble or disperse in water, or in a liquid medium containing water-soluble organic solvent. In addition, the ink composition can further comprise a surfactant, which can modify the properties of the ink, to meet the requirement for the textile ink-jet printing.
U.S. Pat. No. 6,780,229 has disclosed an ink composition, which comprises an organic buffer to maintain the pH value of the ink composition between 4 to 8. U.S. Pat. No. 6,015,454 has disclosed another ink composition, which comprises at least one reactive dye, and 1,2-propylene glycol or N-methyl-2-pyrrolidone, to improve the color strength and fixation. However, this ink composition has a problem in storage stability, durable printing stability, and nozzle clogging. US 2003/0172840 has disclosed another ink composition, which comprises at least one dye, sulfolane, and a buffer system, to prevent the problems of storage stability and nozzle clogging. Unfortunately, the chlorine-resistance fastness, high color strength, and dye solubility of this ink composition are not good enough.
Hence, it is desirable to provide an ink composition for digital textile printing, which exhibits high pH stability, low color deterioration, high color strength, and high dye concentration.